Every ww2 enthusiast (or most of them) has an favorite AFV ot the era.
But don't let the love blinds you - what was the greatest shortcoming (or more of those?) that one could say designers missed their mark?
Of course, you can bash the AFVs you generally dislike, in case your AFV (please state what one is that) is perfect.

In light of recent forum bad blood pi$$ing contest, I'd like to call for a calm discussion.

Some of the Bad ones were deliberate choices due to faulty tactical thinking or doctrine, some were forced on the designers by circumstances of the times. Certain engine or transmission choices for instance. Some were choices forced by "budgets" either money or raw materials (not always the same thing, you may have the money, it doesn't mean you can get a specific element/alloy).

Most nations built light tanks in too great a numbers and for too long at the beginning of the war.
Most nations didn't pay enough attention to vision for the crew and commander.

Panzer II Ausf F was a reliable and inexpensive weapons carrier. However it was too narrow. Soviet Union didn't make that mistake with their similiar size Su-76 weapons carrier. IMO Panzer II Ausf F weapons carrier chassis should be at least 2.48m wide (i.e. similiar to Panzer II Ausf L) and 2.75m would have been ideal.

Mass produce our wider but still inexpensive Panzer II Ausf F chassis from 1941 onward like hot rolls. It has all sorts of uses. These are probably the most useful.
.....10.5cm SP artillery.
.....7.5cm SP AT gun. Can also be used as low cost assault artillery ILO StuG III.
.....Light flak panzer with flakvierling. Turret similiar to historical Wirbelwind. This would replace historical Sd.Kfz.7/1 half track mounted weapon.

For me it has to be any of the Tigers. The Konigtigers were awsome machines with obvious shortcomings, weight, suspensions, fuel consumption, maintainance, etc. and Germany was ill advised to build them but...
The Tiger I's were equally awsome and illustrated German blunt force thinking...penetrate 50mm make it 60mm, 70mm, 80mm, 100mm. Don't consider engines or suspensions, roads, bridges, or railroad gauge. And again the Germans were ill advised to invest so much into them for so little return, but still awesome machines.
The Panthers were probably the best all around tanks though they suffered from many of the same problems. If only the Tiger resources had gone into improving the Panthers.
The Sherman "Tommy-cookers" had to be the worst in the war

Throughout its career, the weakest parts were its final drive units. The problems were from a combination of factors. The original MAN proposal had called for the Panther to have an epicyclic gearing (planetary) system in the final drive, similar to that used in the Tiger I.[35] However, Germany at the time suffered from a shortage of gear-cutting machine tools and, unlike the Tiger tanks, the Panther was intended to be produced in large numbers. To achieve the goal of higher production rates, numerous simplifications were made to the design and its manufacture. This process was aggressively pushed forward, sometimes against the wishes of designers and army officers, by the Chief Director of Armament and War Production, Karl-Otto Saur (who worked under, and later succeeded, Reichminister Speer). Consequently, the final drive was changed to a double spur system.[36] Although much simpler to produce, the double spur gears had inherently higher internal impact and stress loads, making them prone to failure under the high torque requirements of the heavy Panther tank. Furthermore, high quality steel intended for double spur system was not available for mass production, and was replaced by 37MnSi5 tempered steel, which was unsuitable for high-stress gear.[37] In contrast, both the Tiger II[38] and the US M4 Sherman tank had double helical (herringbone gears) in their final drives,[39] a system that reduced internal stress loads and was less complex than planetary geartrains.

Compounding these problems was the fact that the final drive's housing and gear mountings were too weak because of the type of steel used and/or the tight space allotted for the final drive. The final gear mountings deformed easily under the high torque and stress loads, pushing the gears out of alignment and resulting in failure.[40] Due to the weakness of the final drives their average fatigue life was only 150 km. In Normandy, about half of the abandoned Panthers were found by the French to have broken final drives.[27] However, at least the final gear housing was eventually replaced with stronger one, while final gear problem was never solved.[41]

Plans were made to replace the final drive, either with a version of the original epicyclic gears planned by MAN, or with the final drive of the Tiger II. These plans were intertwined with the planning for the Panther II, which never came to fruition because Panzer Commission deemed that temporary drop in production of Panther due to merger of Tiger II and Panther II was unacceptable. It was estimated that building the epicyclic gear final drive would have required 2.2 times more machining work than double spur gears, and this would have affected manufacturing output.

I have several favorites
Valentine and Archer, so British. Valentine was a private venture, it was really too small but in that way they managed to keep the weight down and didn't overload the chasis and engine, so they produced a reliable British battle tank, which was extraordinary in early part of war. Archer same way, ingenious way to cram a 17pdr into so small chassis, again a bit too small, driver's head was in the way but the solution made it almost impossible to missuse it as an ersatz tank by the infantry officers. Also easy to withraw when the situation developed too hot in the current fire position (once the drive got into his place)

Comet, IMHO excellent MTB for early 45, fast and reliable with an excellent gun and reasonable protection. Also being correct size, not too heavy. And it showed that also winners had waepons which were "too late and too few"

Tiger I, surely it was maybe too heavy and was expensive but not being standard issue MBT that wasn't so dangerous. It put fear into hearts of the enemies of the Reich. Of course its weight put great burden on logistics and recovery organization.

Puma and Daimler armoured cars, maybe a bit overgunned for recon vehicles while still being unable to meet late war MBTs even with reasonable chances but they were at least capable to put a hole into side and rear armour of enemy's medium tanks.

Recon vehicles are supposed to remain hidden while sending back a steady stream of intelligence reports.

Counter recon is secondary mission. Light AT weapons are for the purpose of killing enemy recon vehicles.

Fighting enemy MBTs is not part of the recon mission. High speed should be used to evade such threats.

Click to expand...

Daimler ac was there to give support for Dingos (Daimler Scout Car), if they needed heavier fire support of course late in the war there were a couple AMCs (6pdr or 75mm) to help. 2pdr was a bit overkill against normal German recon vehicles. IIRC Puma designed to give A/T support for 222s and 234/1s, 50mm was also a overkill against all other recon vehicles but light tanks but again IIRC Puma was designed as an antidose for those and had some chance against T-34s.

Puma - there's no such vehicle. There's a 234/2. I actually don't know what the intention was with the 5cm gun - overkill for an AC and also influences commanders to go too offensive. The fire support AC were 233 and 234/3.

Tomo, Best/Worst is always opinion based. Is a knife better/superior to a gun? Depends.
Production of the Sherman was favored by the commander of the Armored Ground Forces, Gen. Lesley J. McNair over the heavier M26 Pershing, which resulted in the latter being deployed too late to play any significant role in the war. McNair, an artilleryman, championed the tank destroyer within the U.S. Armored Forces. Tanks were to support the infantry, exploit breakthroughs, and avoid tank-to-tank battles. Enemy tanks were to be engaged by the tank destroyer force, composed of a mix self-propelled tank destroyers and towed antitank guns. The tank destroyers were supposed to be faster and carry a more powerful anti-tank gun than tanks since armor was sacrificed for speed. The tank destroyer doctrine played a large role in the lack of urgency in improving the firepower of the M4 Sherman, as the emphasis was on its role as infantry support. McNair opposed development of the M26 and other proposed heavy tanks during the crucial period of 1943 because he saw no "battle need" for them. In mid-1943, Lt. General Devers, commander of U.S. forces in the European Theater of Operations asked for 250 M26s for use in the invasion of France. McNair refused. Devers appealed to General George Marshall, the Army Chief of Staff. Marshall summarily ordered the tanks to be provided as soon as they could be produced. Soon after the Normandy invasion, General Dwight D. Eisenhower urgently requested the M26 Pershing, but McNair's continued opposition delayed production. General Marshall intervened again and the tanks were eventually brought into production. However, only a few saw combat and were too late to have any effect on the battlefield.
The M4A1 Sherman first saw combat at the Second Battle of El Alamein in October 1942 with the British 8th Army. The first U.S. Shermans in battle were M4A1s in Operation Torch the next month. At this time, Shermans successfully engaged German Panzer IIIs with long barreled 50 mm L/60 guns, and Panzer IVs with short barreled 75 mm L/24 guns. The M4 and M4A1 were the main types in U.S. units until late 1944, when the Army began replacing them with the preferred M4A3 with its more powerful 500 hp engine
Encounters with a company of Tiger Is, with their heavier armor and 88 mm L/56 guns, in Tunisia were a disaster for the Shermans, however, the fearsome quality of a few German heavy tanks and their crews could sometimes be overcome by the quantity and mobility of the Shermans, supported by artillery and airpower, but at a great cost in U.S. tanks and crewmen. By June 1944, the Panzer IV had been up-gunned with a 75 mm L/48 weapon, and the 75 mm Shermans were outgunned on a regular basis. As a result, the M4A1, was upguned to the 76 mm gun in July 1944, closely followed by the M4A3
In typical Army fashion the new 76mm and 90 mm anti-tank guns were rejected by McNair as “unnecessary”.
In 1943, most German AFVs mounted a 7.5 cm KwK 40. As a result, even weakly armored light German tank destroyers such as the Marder III, which was meant to be a stop-gap measure to fight Soviet tanks in 1942, could destroy Shermans from a distance. The U.S. 76 mm proved comparable in penetrating power to the 7.5 cm KwK 40, however transfer of the upgunned tanks to the front started slowly, and most tanks still had M3's, even by the time of Operation Cobra.
The bigger 76 mm gun could penetrate roughly 88 mm of armor at 1000 m. This was enough to reliably penetrate a PzIV's glacis. However, the 76 mm was not powerful enough against the frontal armor of a Panther. Due to its angle, the Panther's glacis gave it an effective thickness of 140 mm. Therefore to effectively engage a Panther the Shermans had to get relatively close. Additionally the low-flash powder of the Panther made it harder to spot. While firing from range, the Sherman's high flash powder made their shots easy to spot. The Sherman’s gun sights were fixed magnification as compared to the German's multiple magnification settings with added anti-glare filter. U.S. tank units who were engaged at range from German defensive positions sometimes took 50% casualties before even spotting where the fire was coming from. The British-developed Sherman Firefly was an M4 re-gunned with their QF 17 pounder anti-tank gun. The 17 pounder was a 76 mm gun and had a 55 caliber barrel, but introduced a much bigger charge which allowed it to penetrate 140 mm sloped at 30 degrees at 100 m and 120 mm at 1000 m. This gun allowed the Firefly a slight firepower advantage over the Panther, however the muzzle flash due to unburnt powder from the increased charge left crews momentarily blinded after firing. In late 1943, the British offered the 17 pounder to the U.S. Army for use in their M4 tanks since the 17 pounder could be mounted in a standard M4 turret while the U.S. 90 mm gun would need a new turret. General Devers insisted on comparison tests between the 17 pounder and the U.S. 90 mm gun. The tests seemed to show that the 90 mm gun was equal to or better than the 17 pounder. By then, production of the 76 mm M4 and the 90 mm M36 tank destroyer were both underway and U.S. Army lost all interest in the 17 pounder.
In terms of mobility the M4 was criticized by its crews for inability to pivot turn, limiting its usefulness against pivot-turning Panthers. This deficiency was partially compensated by the faster traverse of its turret. The U.S. Army restricted the Sherman's height, width, and weight so that it could be transported via typical bridges, roads, and railroads. This aided strategic, logistical, and tactical flexibility. The Sherman’s speed and cross country performance was indeed superior to the first generation German tanks such as the PzKfpw. III IV, actual comparative testing with the second generation German tanks (Panther Tiger) conducted by the Germans at their Kummersdorf testing facility as well as by the US 2nd Armored Division, proved otherwise.
Lieutenant Colonel Wilson M. Hawkins of the 2nd AD wrote:
"It has been claimed that our tank is the more maneuverable. In recent tests we put a captured German Mark V [Panther] against all models of our own. The German tank was the faster, both across country and on the highway and could make sharper turns. It was also the better hill climber"
Technical Sergeant Willard D. May of the 2nd AD wrote:
"I have taken instructions on the Mark V [Panther] and have found, first, it is easily as maneuverable as the Sherman; second the flotation exceeds that of the Sherman"
Staff Sergeant and Tank Platoon Sergeant Charles A Carden reports:
"The Mark V [Panther] and IV [Tiger] in my opinion have more maneuverability and certainly more flotation. I have seen in many cases where the Mark V and VI tanks could maneuver nicely over ground where the M4 would bog down. On one occasion I saw at least 10 Royal Tigers [Tiger B] make a counter attack against us over ground that for us was nearly impassible"
The Sherman was one of the first widely produced tanks to feature a gyroscopic stabilized gun and sight. The stabilization was only in the vertical plane, as the mechanism could not slew the turret. The utility of the stabilization was debatable and some operators disabled the stabilizer
The Russian T-34 is often credited for introducing sloped armor in a production tank however one can easily see that the Sherman's upper hull was angled at 56 degrees, while the lower half of the hull was curved. The steel frontal turret armor of the M4 ranged from 64–76 mm. The M4’s gun mantlet was also protected by 76 mm of armor sloped at 30 degrees. The turret side armor was 50 mm at 5-degree angle while the rear was 64 mm at a 90-degree angle and the turret roof was 25 mm thick. The hull front sported 51 mm armor. Perhaps the most telling report on the armor of the Sherman compared to the Panther can be described by statements used in a report to General Eisenhower at SHAEF: “I have actually seen ricochets go through an M4 at 3000 yards. I have seen HEAT fired from a 105mm Howitzer at a Panther at 400 yards. The track was hit and damaged, and a direct hit on the turret only chipped the paint.”
The worst fault of all is what happened after the Sherman’s inadequate armour was penetrated. The Sherman quickly gained grim nicknames like "Tommycooker” by the Germans. While the British took to calling it the "Ronson", the cigarette lighter which had the slogan "Lights up the first time, every time!" Polish tankers referred to it as "The Burning Grave”. Research conducted by the British No. 2 Operational Research Section, after the Normandy campaign, concluded a Sherman would be set alight 82% of the time following an average of 1.89 penetrations of the tank’s armor. United States Army research proved that the major reason for this was the stowage of main gun ammunition in the sponsons above the tracks. At first a partial remedy to ammunition fires in the M4 was found by welding 1-inch-thick armor plates to the sponson sides over the ammunition stowage bins. Later models moved ammunition stowage to the hull floor, with additional water jackets surrounding the main gun ammunition stowage. The practice, known as "wet stowage", reduced the chance of fire after a hit by a factor of four.[

Mikewint, you are spot on as far as the "Tommy cooker" or "Ronson" names given to the Sherman. A lot of people beieve it was due to them being petrol driven and this being the cause for the inferno when hit.
It was not this at all. It was as you correctly stated the fact that the ammo stowage was highly succeptible to ignition when the tank was hit. The crews believed (incorrectly) that additional armour was required - but it was only with the addition of water jackets that the tanks improved their ability to survive a hit.
If the Allies had not had the quantity of Shermans during the various campaigns, then the outcome could well have been different.
It was not the perfect tank, but it was versatile and most importantly available in quantity.

Now about issues, or 'issues':
-Any tank would burn if the ammo is ignited, not just Sherman. Once the wet ammo storage was introduced, that horror story was over
-The wide tracks were introduced in 1944, so the ground pressure went down
-Nair's management of tank TD fleet has nothing to do with M4's perceived faults, only points out that M4 was able to have 76mm sooner and/or more often than historically
-The tank was been able to be up-gunned with premium AT gun
-It was also able to carry another 6 tons of armor, while still being movable enough, you can check out here: M4A3E2 Sherman

As for 'seeing ricochets going through M4 from 3000 yards' - even if Dwight made such comments, do you really believe that was the case? If an AP round is that powerful, it would pierce the T-34, or Cromwell, let alone Pz-IV. The 105mm HEAT being unable to penetrate Panther? Yet Panzerfaust was able to pierce IS-2, featuring even ticker armor.
My take is that Eisenhower was using tough talk in order to get the M26 in Europe, since the medium tank, no matter how good, was never going to win vs. a good heavy tank 1:1.
That M4 gave a sterling service in NA and Russia should not been overlooked here, too.

Tomo, I once thought how geat it would be to be a tanker, riding around, not having to slog through the bush, protective armour, and ALL THAT WATER!!! Then I saw my first tank hit by a rocket. Changed my mind quick. So to me the choice is simple: Would you like to hop in a Sherman to face a Tiger or hop in a Tiger to face a Sherman?

Isn't that unfair, to compare the tanks of different sizes, classes, and availability? Was it M4's (and it's designers) fault that US Army wanted/needed/had to make do with a 30 ton tank, and not the 40-50-60 ton one?

Back in 1995, our army made a sweeping dash from mountain sides into the Serb-held Knin area. You should see the ravines and like, we (the infantry) have had a tough time to march through that. Yet our T-55s (yep, the ones even Malyutka can pierce through, no problems; 36 ton tanks) were managing through, no problems. So maybe it would be either T-55s, or no tanks at all, so we (the infantry) would need to do heavy lifting.

Tomo, while I understand your point, good - bad - better - worst are relative terms. The Sherman was the U.S. Army's MBT in WWII. As such it had to face the likes of the Panther, Tiger, and Konigtiger. Unfortunately there were no referees to call the match because of the unfairness of matching a medium against a heavy weight.
Therefore it is fair to see how they match-up against each other since in the real world they indeed match up against each other.
The Tigers were marvels of engineering but the time, energy, materials used up helped the Germans to loose the war not win it. If the Tiger/Sherman kill ratio was 1:20 the Tiger looses since the US could easily and quickly relace the 20 Shermans with 30 Shermans. Superior weapons cost the Germans the warf

Some countries over reached with their next generation/s of tanks. Some under-reached. Staying status quo was going to leave you behind even the under-reachers. The Sherman was an excellent tank when it came out in the summer of 1942. Thinking that it would still be a first class tank without any major improvements in the summer of 1944 is depending on your enemy not to make any improvements or introduce new models.

Conversely the Germans could not depend on the Americans, British and Russians NOT to improve their tanks.